This invention relates to a flow-divider regulator, also sometimes called an unloading valve, for use in a hydraulic system for a vehicle to enable its use with open-center and closed-center control valves and apparatus.
As is well known in the art, the flow divider of this type operates to divide a single pump discharging flow in a suitable predetermined ratio and provides for the smaller regulated portion of flow to be delivered to a hydraulic system which might be such a thing as the known-power braking booster, while the major unregulated remaining portion of the pump flow continues to pass through the other system, such as for example, the known open-center power steering gear valve, and the operation of either system does not affect the behavior of the other.
In the use of the flow divider, a relief valve is needed to be equipped on a discharging line from the pump for safeguarding the pump against the possibility of ruin due to an unrestricted increase in pressure within its discharging line, when the hydraulic systems are extremely actuated to thereby stop fluid flow therethrough followed by the unrestricted pressure rise in the discharging line.
Contradictorily to the intended character of the relief valve, the same should be normally held inactive in order to maintain at least continued remaining pump flow portion to one of the systems, even though the other regulated flow ceases owing to an extreme actuation of the other system causing an increase in pressure as would open the relief valve. This is required for safety purpose, since the real action or opening of the relief valve will result in escaping of the pump flow rather into the reservoir than the said one of the systems.
In order to keep the relief valve inactive or closed for preserving a continued flow of the major portion, in case of the cessation of flow, it has been the practice in the art that an additional or second relief valve is further provided on the regulated pump flow line for the sake of limitation of pressure rise therein to a lower level than that predetermined by the first relief valve, so that the major remainding pump flow is ensured through the said one of the hydraulic systems.
The provision of the additional relief valve is considered to be a defect in that, it would represent a substantially greater cost owing to a resulting structural complication.
A solution is now demanded to provide means for avoiding necessity of the second or additional relief valve on the regulated pump flow line leading to the said other system.